Find how much a wire stretched at the bottom of swing of pendulum

[rezihk]

1. A building is to be demolished by a 400kg shell ball swinging on the end of a 30.0 m steel wire of diameter 5.00 cm hanging from a tall crane. As the ball is swung though an arc from side to side, the wire makes an angle of 50° with the vertical at the top of the swing. find the amount by which the wire is stretched at the bottom of the swing



2. stress=F/A, strain=ΔL/L, F=ma, Y= Young's Modulus



3. ΔL=F/A*L/Y

 

[vivekrai]

I suppose you have the problem at finding the force. User Energy conservation to find the velocity at the lowermost point. Then use the equation T-mg = mv^2/(L+ΔL)

 

[issacnewton]

vivek, let the guy show some work at least. that's the forum policy. the person has not shown ANY work.

 

[rezihk]

i figured out all these values and plugged them into the eqn i have:

A=1.96E-3 m^2 wire
Y=20E10
L=30m
Tension if it were at rest and bottom: T=mg=3924N
and got dL=0.03cm
but I'm assuming at it stretches the same if it were at rest or accelerating when at the bottom
how do i take acceleration into account?